1. Field of the Invention
This invention relates to electric power distribution systems such as those found in residential or light commercial applications in which circuit breakers can be reclosed from a remote location using power line communications.
2. Background Information
Circuit breakers are commonly used to provide both main and branch circuit protection in homes and light commercial applications. The breakers are mounted in enclosures called load centers which are normally placed in non-intrusive locations such as basements, garages, and the like, as they usually do not require maintenance or attention. A circuit breaker is an automatic device which will trip or open immediately should an overcurrent (short circuit or overload) occur in the protected circuit. Such a condition should be, and in fact must be, corrected before the circuit breaker can be reset to reestablish the circuit. These circuit breakers also respond to overload conditions which can occur for instance when too many loads, such as several appliances, are energized by the same branch circuit. Such overloads can dangerously overheat the branch circuit wiring if permitted to continue on, but the circuit breaker responds to persistent overloads by tripping open. The overload condition can be corrected by reducing the load on the protected circuit and it is then safe to reclose the circuit breaker.
There is a growing interest in providing protection against arcing faults which can occur due to abused or damaged cables/wires/cords. For instance, when an extension cord is cut or becomes worn and in other circumstances where bared conductors of opposite polarity come into temporary or permanent contact or breaks occur in wiring. Electronic circuits respond to such faults and trip the circuit breaker. Again, the circuit breaker can be reset after the faulty cord is disconnected or the arcing condition is otherwise terminated. Electronic trip circuits are also available for tripping the circuit breaker open in response to ground faults. Once this condition is cleared it is also safe to reclose the circuit breaker.
Currently it is necessary to go to the load center to reset a tripped circuit breaker. As mentioned, the load center can be in the basement or in some other isolated location within the house or building. It is sometimes difficult to identify the tripped circuit breaker from among the numerous circuit breakers housed side by side in the load center. In addition, the lighting at the load center could be on the tripped circuit thereby making it more difficult to locate the correct circuit breaker.
U.S. Pat. No. 5,373,411 discloses a residential circuit breaker which incorporates a solenoid operated switch in series with the circuit breaker contacts. The switch allows the branch circuit to be energized and deenergized at the load center from a remote location. However, the switch can only be used to open and close on normal currents below the rated current of the circuit breaker. The circuit breaker stills responds to short circuits and overloads to interrupt current flow by tripping open. The tripped circuit breaker is not remotely resettable. It still requires manual operation at the load center. Furthermore, additional wiring is required between the solenoid of the switch and the remote location.
There is a need, therefore, for an improved electric power distribution system such as for residences and light commercial applications in which tripped circuit breakers can be reset remotely.
There is a particular need for such a system which can be adapted to present power distribution systems easily and economically.
In particular there is a need for such an improved power system which requires no additional wiring.